When is it ethical to randomly determine the provision of a treatment to people in an experiment? Researchers designing such experiments often appeal to the principle of equipoise, which means “that there is genuine uncertainty in the expert medical community over whether a treatment will be beneficial.” This principle captures a straightforward ethical logic: we know that ARVs are effective in treating AIDS, so it would be unethical to design an experiment that denies some AIDS patients access to ARVs. In contrast, until recently we did not know that starting ARVs immediately had health benefits for people with HIV who do know yet have AIDS. The experiment that proved that this was the case was entirely ethical to conduct.

This approach works well for medical trials, because doctors have the joint social roles of studying which treatments are effective and actually providing people with the treatments that work. Social scientists tend to be in a very different situation. First, relative to medical research, we are substantially less sure what the impacts of various interventions will be.** Second (despite what people might think about economists in particular) we just don’t have that much influence. There are many policies and programs that economists know to be effective that have little or no traction in terms of actual policies. An example that I am particularly fond of is the idea that if you want to maximize uptake and use of a product, you should give it away. The notion that people won’t “value” things they get for free is so popular that two economists actually had to go out and randomize prices for insecticide-treated bednets to prove that giving them away would work for fighting malaria. And still, I see people charging money for them.

The bednet study is a great example of what I am dubbing practical equipoise. I personally had no doubt, prior to that study, about which direction the demand curve for bednets sloped. Almost any economist would probably have felt the same way, so “clinical equipoise” did not hold. Yet policymakers felt strongly that user fees for the nets were a great thing. Practical equipoise is a situation where the science is in but policymakers don’t agree with it; while the scale of knowledge is not balanced, we can try to use persuasion and facts to balance the scale of actual practice. In this situation, randomized experiments are an ethical imperative – they benefit people who would otherwise have lost out, and also can help promote universal access to beneficial treatments in the future.